Fix incorrect change of my_view_mode_quantity ProxyField which must point to Base_viewFieldLibrary/my_view_mode_quantity so that figure CSS class is applied (9fcbe9c).
TODO: Revert "Portal Types Roles defined in the current bt5 should be usable (followup of dd77599)."

This reverts commit c3b1def30fb709194ec2a80b0734431704409686:

* skin after paths, because we can install a custom connection string as path
  and use it with SQLMethods in a skin (see comment).

* This does not work with erp5_jquery as it uses PathTemplateItem to add a
  skin, but with the reverted commit, SkinTemplateItem was installed before
  PathTemplate, thus raising a KeyError (RegisteredSkinTemplateItem).